An efficient approach to model distortion in weakly nonlinear Gm - C filters

Standard wireless communication circuits extensively use bandpass G
m
-C filters, whose Total Harmonic Distortion (THD) and Intermodulation Distortion (IMD) have been estimated and modeled previously. However previous approaches have considered only third order nonlinearity effects assuming fully balanced OTAs. This assumption does not hold good for practical circuits. Hence a structural modeling approach which takes into consideration all perceptible orders of nonlinearity has been proposed. The proposed approach abstracts the nonlinear elements from the G
m
-C filter and models them using a macro-modeling technique. Results from the proposed model are found to be in good agreement with a designed weakly nonlinear G
m
-C filter with a 4 times improvement in simulation time. Extension of the approach to the case of a lossy integrator shows improved accuracy over existing modeling approaches.